Tbi conversion questions

[BowTieJockey]

Some of these questions may have been answered but I can't find them anywhere , I've been searching online for 2 or 3 days.

Let me start of with saying that I have an 84 single cab 4x4 Silverado, so it has all the bells and whistles. I'm looking to install a stock oem 87 tbi harness, now I k or I can't just pull the harness and ecm and install it. I've got tank,fuel lines and full tbi motor already. I'm trying to figure it the wiring. I thbk I have found a harness but the guy still drives the truck so I'd have to be gentle. In order to just get the tbi harness and ecm would it effect his truck at all? If so what would I have to leave behind? Can I get it all out without taki g alert his whole truck? What I'm looking at doing is pulling just the tbi stuff out, minus his tank and its wiring. If it turns out that I can get his tbi stuff, what should I be expecting going in? I deffinatkey don't want to tie up hos truck for three days. I also have another option. I can get a free tbi harness out a 92 blazer my dad is scraping how much work is involved in adapting it to my truck. I want a drop in system but can deal with adapting it if it's not a whole lot of work. Thanks in advance. I hope I can get this figures out soon.

 

[Jims86]

So, just to be clear:
You already have a TBI engine with TBI injection unit, proper drivers side exhaust with o2 sensor provision, ESC module, MAP sensor, EGR and solenoid, Electronic distributor?
If so, all you need is the TBI Harness, ECM, and the fuel pump relay on the firewall.
I recommend pulling the cavity connector under the brake booster, unbolt grounds from behind the Engine...like at the rear of the heads, and at the water neck. Carefully inplug the connector under the dash, and disconnect the ECM, carefully rout the plugs ot of the firewall one at a time. you may have to turn the ecm plugs sideways. then of course, grab the ECM.

I would recommend leaving your current 84 charging and starting system in tact, and modify and install the 87 harness.

 

[BowTieJockey]

Yes I do have the complete engine . I pulled it myself. So if I remove the 87 harness of that truck I will have to unplug stuff from the connector behind the fuse box? When I remove the harness will It take anything essential for his truck to run a carburayed motor. I would prefer to stay away from under the dash in the driver's side. Does all the tbi harness come out of the passenger side holes on the fire wall or does it come out and the driver's side to?

 

[Jims86]

Yes I do have the complete engine . I pulled it myself. So if I remove the 87 harness of that truck I will have to unplug stuff from the connector behind the fuse box? When I remove the harness will It take anything essential for his truck to run a carburayed motor. I would prefer to stay away from under the dash in the driver's side. Does all the tbi harness come out of the passenger side holes on the fire wall or does it come out and the driver's side to?

A few wires(4 IIRC) come from the cavity on the drivers side. you have no choice but to go on the passenger side.
For the truck to run carbed, you will have to open the 87 harness, and separate the charging and starting system wires, and leave them when you pull the fuel injection harness.

 

[BowTieJockey]

Seems easy enough.

I thought of something else today, did gm ever put a 4l80e behind a tbi engine. If they did I'm pretty sure it was in the Gmt400 era right? So if this is possible couldn't I steal an ecm and 4l80e from one of these trucks and run the 80e and my 5.7 with a Gmt400 ecm with my 87 harness.

 

[foamypirate]

Seems easy enough.

I thought of something else today, did gm ever put a 4l80e behind a tbi engine. If they did I'm pretty sure it was in the Gmt400 era right? So if this is possible couldn't I steal an ecm and 4l80e from one of these trucks and run the 80e and my 5.7 with a Gmt400 ecm with my 87 harness.

91' Burbs (squarebody variety) could have a 4L80E and TBI.

 

[BowTieJockey]

91' Burbs (squarebody variety) could have a 4L80E and TBI.

Sounds tough to find. I wish I had a list of what came with this setup. I wonder if I should ask Retro?

 

[foamypirate]

Sounds tough to find. I wish I had a list of what came with this setup. I wonder if I should ask Retro?

I'm sure, like you said, you could modify a harness (or maybe even use it straight up) from a GMT400 with TBI and a 4L80E. Those would be easier to find, just wanted to let you know that a Squarebody option is out there.

 

[BowTieJockey]

I'm sure, like you said, you could modify a harness (or maybe even use it straight up) from a GMT400 with TBI and a 4L80E. Those would be easier to find, just wanted to let you know that a Squarebody option is out there.

It's not something I'm planning on doing right now I just wanted to see if it was possible so I can keep my eyes peeled for one so I can snag the harness especially if it's cheap

 

[BowTieJockey]

Did a little more reaserch. And just wow I'm in way over my head on this, I'm so confused. If I were to get the harness and ecm out of a tbi 4l80e truck couldn't I just plug it into an existing tbi harness in my truck and plug in a transmission harness and install the transmission. Or is it something like cutting off the ecm plugs and running tranny wires then putting it all in a plug then into the new ecm?

 

[BowTieJockey]

What would have to be don't to use a 454 tbi ecm with a 350

Sent from my HTC6500LVW using Tapatalk

 

[Joshua8336]

lt1swap.com

 

[Jims86]

A later model 4l80e would be a smart investment, But I would recommend using a PCM and Harness from A 94-95 TBi 350, much better driveabilty, and more common than the 91 version.

 

[BowTieJockey]

I have done some research and have come to the conclusion that gm did in fact use a 5.7 tbi and 4l80e pair. (Not in these trucks) so I know I'll need to look for 3/4 and 1 ton Gmt 400s earlier than 96? Did gm ever use anything other than 80e transmissions in them? How hard is it to remove just the tbi side of the harness from a Gmt400 truck?, can I just unplug the ecm and everything from the engine and transmission and take the ecm or is there any wires that go other places?

Thanks for any help guys, I need to know all of these answers so that when I go on the hunt for one I can know what to expect and be looking for?

Posted from my phone in my lap during class